The present invention relates generally to a device for transmitting and receiving light, radio wave or similar electromagnetic waves and, more particularly, to an electromagnetic wave transmitting/receiving device that detects or radiates electromagnetic waves with a high degree of accuracy in their angle of incidence and emittance.
In an electromagnetic sensor or antenna it is an important problem to accurately control the direction of electromagnetic waves.
Conventionally, a dielectric lens is used to control the directivity of electromagnetic waves. A dielectric lens antenna using such a dielectric lens is described in Japanese Patent Application Kokai Publication No. 2000-174547 (published Jun. 23, 2000, hereinafter referred to as document 1). In the dielectric lens antenna disclosed in document 1 the dielectric constant of a dielectric member, which is disposed between the dielectric lens and the primary radiator to integrate them into a single structural member, is gradually reduced, for instance, toward radially outer side of the dielectric lens with a view to achieving high efficiency and sliming down of the antenna. On the other hand, in Japanese Patent No. 2768439 (issued Jun. 25, 1998, hereinafter referred to as document 2) there is set forth a method for detecting electromagnetic waves of low directivity over a wide angle range by a plurality of directional antennas placed in different directions.
The dielectric lens antenna disclosed in document 1 can be slimmed down as compared with those used in the past, but the bulkiness of the dielectric lens itself imposes limitations on the sliming down of the antenna structure, and the detection of the angle of electromagnetic waves generally calls for arrangement of a plurality of dielectric lenses; for these reasons, slimming down or miniaturization of the dielectric lens antenna is hard to realize.
With the structure using a plurality of directional antennas as set forth in document 2, enhancement of the accuracy of angle detection of electromagnetic waves requires arrangement of a large number of antennas, and hence miniaturization is difficult to achieve.